Vesta Asteroid’s Spectra Unveiled

The first close-up view of Vesta, one of the largest asteroids in our solar system at about 330 miles in diameter, reveals a mix of complex silicate minerals on its surface that confirm Vesta is the source of so-called howardite-eucrite-diogenite meteorites found on Earth (Science, DOI: 10.1126/science.1219270). NASA’s Dawnspacecraft launched in 2007 and reached Vesta last July. Initial visible and infrared spectra from Dawn show that Vesta’s surface is composed of variable amounts of eucrites and diogenites. The data are consistent with the theory that the asteroid body formed, melted into magma from heat generated by radioactive decay, and then cooled, reports a group led by M. Cristina de Sanctis of Italy’s National Institute for Astrophysics. Although the data indicate the magma separated into a eucrite-rich upper crust and a diogenite-rich lower crust, mixtures and variation of the two mineral families across the asteroid mean that further study is needed to obtain the complete picture of how Vesta formed and geologically evolved, the team says.